Engine damper bypass for hybrid powertrains

1. A powertrain comprising:

an engine having a crankshaft;

a transmission having an input member;

an electric motor/generator operatively connected to the transmission input member and configured to selectively transmit torque thereto;

a damper operatively interconnecting the input member and the crankshaft;

a damper bypass system operatively connected to the crankshaft and the input member;

wherein the damper bypass system is configured to never transfer torque from the crankshaft to the input member; and

wherein the damper bypass system is configured to transmit torque from the input member to the crankshaft in response to input member torque exceeding crankshaft torque.

2. The powertrain of claim 1 , wherein the damper bypass system includes a one-way clutch that operatively interconnects the crankshaft and the input member.

3. The powertrain of claim 2 , wherein the one-way clutch includes an outer race mounted with respect to one of the crankshaft and the input member for rotation therewith, an inner race, and a plurality of sprags between the inner race and the outer race.

4. The powertrain of claim 3 , wherein the sprags are configured such that rotation of the outer race causes the sprags to be wedged between the inner race and the outer race thereby to transmit torque from the outer race to the inner race.

5. The powertrain of claim 4 , further comprising a plurality of release tabs that are operatively connected to one of the crankshaft and the input member for rotation therewith;

wherein each of the release tabs extends between two of the sprags.

6. The powertrain of claim 5 , wherein the release tabs are configured to prevent the sprags from wedging between the inner race and the outer race when the torque on the release tabs exceeds the torque on the outer race.

7. The powertrain of claim 2 , wherein the electric motor/generator is part of the transmission.

8. A powertrain comprising:

an engine having a crankshaft;

a transmission having an input member;

an electric motor/generator operatively connected to the input member and configured to selectively transmit torque thereto;

a damper operatively interconnecting the input member and the crankshaft;

a damper bypass system including a bidirectional one-way clutch and operatively connected to the crankshaft and the input member;

wherein the bidirectional one-way clutch is configured to never transfer torque from the crankshaft to the input member; and

wherein the bidirectional one-way clutch is configured to transmit torque from the input member to the crankshaft in response to input member torque exceeding crankshaft torque.

9. The powertrain of claim 8 , wherein the bidirectional one-way clutch includes an outer race mounted with respect to one of the crankshaft and the input member for rotation therewith, an inner race, a first plurality of sprags between the inner race and the outer race, and a second plurality of sprags between the inner race and the outer race.

10. The powertrain of claim 9 , wherein the first plurality of sprags are configured such that rotation of the outer race in a first direction causes the first plurality of sprags to be wedged between the inner race and the outer race thereby to transmit torque from the outer race to the inner race; and

wherein the second plurality of sprags are configured such that rotation of the outer race in a second direction opposite the first direction causes the second plurality of sprags to be wedged between the inner race and the outer race thereby to transmit torque from the outer race to the inner race.

11. The powertrain of claim 10 , further comprising a plurality of release tabs that are operatively connected to one of the crankshaft and the input member for rotation therewith;

wherein each of the release tabs extends between one of the sprags in the first plurality of sprags and one of the sprags in the second plurality of sprags.

12. The powertrain of claim 11 , wherein the release tabs are configured to prevent the sprags from wedging between the inner race and the outer race when the torque on the release tabs exceeds the torque on the outer race.